The superior colliculus is involved in orienting and attending to visual and somatosensory stimuli. This behavioral role is subserved primarily by intermediate-deep laminae cells. Yet surprisingly, most of the work done on the superior colliculus has focused on superficial lamina visual cells. Thus, we know comparatively little about the manner in which sensory information is processed in the cells that appear critical for the superior colliculus to play its role in orienting to and localizing sensory stimuli. Of primary concern in the present proposal is how the receptive fields and response properties of these intermediate-deep lamina cells are formed from the integration of various ascending and descending inputs. In the past few years, we identified the source of descending (corticotectal) somatosensory input as the anterior ectosylvian sulcus (AES) and the rostral suprasylvian sulcus. A "new" somatosensory cortex in the AES was described and labeled SIV. Both the AES and the rostral supra-sylvian sulcus have also been shown to contain visual cells, and both regions project widely across the intermediate-deep laminae of the superior colliculus. In the proposed experiments, we will conduct an extensive series of experiments to document the normal response and receptive field properties of deep lamina visual, somatosensory and visual-somatosensory (bimodal) cells. We will then determine what contributions are made to these properties by the visual and somatosensory corticotectal afferents received from the areas described above. These data are necessary to (a) give us a comprehensive view of the properties of these intermediate-deep laminae cells, (b) provide insight into how these properties are built from the signals of specific afferents, and (c) afford us the opportunity to compare the properties of visual and somatosensory cells in the same structure that may underlie the same types of behavior. These data are crucial if we are to gain insight into which neuronal properties are essential for which behaviors, and to make progress toward closing the conceptual gap between neurophysiology and behavior.